Re: [R] selecting maximum values

From: Sean Davis <sdavis2_at_mail.nih.gov>
Date: Thu 05 May 2005 - 02:12:06 EST

see ?aggregate.

Sean

On May 4, 2005, at 11:43 AM, alessandro carletti wrote:

> Sorry for disturbing you with another newbie question!
> I have a data frame about coastal waters quality
> parameters: for some parameters (e.g. NH3) I have only
> 1 observation for each sampling station and each
> sampling date, while in other cases (chlorophyll) I
> have 1 obs for each meter-depth for each station and
> date. How can I select only the max chlorophyll value
> for each station/date?
>
> example
>
> row station date depth chlorophyll
> 1 Castagneto 21/06/01 -0.5 2.0
> 2 Castagneto 21/06/01 -1.5 2.2
> 3 Castagneto 21/06/01 -2.5 2.4
> 4 Castagneto 21/06/01 -3.5 2.1
> 5 Ancona 23/06/01 -0.5 2.4
> 6 Ancona 23/06/01 -1.5 2.5
> 7 Ancona 23/06/01 -2.5 2.2
> 8 Ancona 23/06/01 -3.5 2.1
> 9 Ancona 23/06/01 -4.5 1.9
> ...
>
> I'd like to select only row 3 and 6, the ones with max
> chlorophyll values, or have the mean for the rows 1:4
> and 5:9
>
> Thanks
>
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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu May 05 03:00:01 2005

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